#define _CRT_SECURE_NO_WARNINGS 1
bool isUnivalTree(struct TreeNode* root) {
	if (root == NULL)
		return true;
	if (root->left && root->left->val != root->val)
		return false;
	if (root->right && root->right->val != root->val)
			return false;
	return isUnivalTree(root->left) && isUnivalTree(root->right);
}
